Dimple die heater



Feb- 26, 1957 J. R. GuNTHl-:R ET AL DIMPLE DIE HEATER 2 Sheets-Sheet l Filed Dec. 10, 1954 Feb- 26, 1957 J. R. GUNTHER ET AL 2,783,363

DIMPLE DIE HEATER Filed Dec. 1o, 1954 2 sheeheet 2 Jg. L-

simultaneously cause operation of piston-cylinder 21 in its rst or low pressure stage. The punch 19 is thereby urged toward die 18 with the sheet metal therebetween. The first stage pressure is sufliciently low that no deformation of the sheet results. The dmpling members 18, 19 are however snugly pressed against the metal and are in good heat transfer relation therewith. The rst stage of pressure is maintained by a suitable combined temperature-time delay mechanism, forming a portion of control 22, until the sheet metal is heated to the necessary predetermined temperature. When this condition is attained, piston-cylinder 21 enters its second or high pressure stage in which the sheet material is permanently deformed by the mating dimpling members 1S, 19. After the dimpling is achieved, piston-cylinder 21 is operated in a reverse direction to withdraw punch 19. The sheet then may be reoriented and the above steps repeated to dimple about other rivet openings or holes.

Now with reference to Figure 2, the essential details of the lower die l and upper punch i9 are shown, incorporating the novel features of this invention. Lower die 1S includes a platform 25 having an aligning bore 27 centrally located therein and a depending mounting post 2S. The post 28 is adapted to be mounted in a complementary opening in pedestal 15. Expansion clip 29 on post 28 is arranged to engage within a circumferential recess in the pedestal opening to releasably secure the platform on the pedestal 15.

Removably atlixed upon platform 25, as by a plurality of screw fasteners, one of which is shown at 32, is a metallic flanged spool 33 having a shouldered bore 34 extending axially therethrough. In order that the spool 33 may be properly oriented with respect to platform 25, a dowel 35 of appropriate length is positioned in aligning bore 27 and extends into the lower portion of bore 34 in spool 33. For a purpose hereinafter set out, as best seen in Figure 4, there is an integral, diametrically extending die support 37 projecting upwardly from the anged spool 33, the bore 34 also extending through the die support 37. The female die element 39 rests on support 37 and has a post 4l) fitting within the upper end of bore 34. The die 39 is maintained on support 37 by means of a spring clip 42 which exerts a radial biasing force thereagainst.

The upper punch 19 is similar in construction to that of lower die 1S as thus far defined and includes platform 44, with its post 45 and expansion spring 46, flanged spool 48 and punch element 50. The only distinction between upper and lower spools 33, 48 is that the upper spool does not include a projecting punch support but rather die 50 directly abuts the lower flange of spool 4S. However, as will later be seen, the projecting die support 37 is a feature enabling the machine to be used on certain shapes of stock material and may be omitted when dimpling is to be performed on flat sheet metal.

Since the heating components in the upper and lower assemblies 18, i9 are identical in construction and function, like reference numerals will be used to designate the corresponding parts therein now to be described with respect to lower spool 33. Concentrically wrapped around the core and between flanges 51 of spool 33 are several turns of a heating element constituting coil 52 which, by way of example, may be made of a steel sheathed Nicrome wire. Electrical current is applied to the coil 52 through leads 53 and is regulated by controls 22. To enclose coil 52 within spool 33 an integral sheath 55 is wrapped about anges 51 and is seated within circumferential grooves 56 therein. In order to reduce shock hazard and to protect lead-ins 53 from excessive heat, sheath 55 is fabricated with extensions 57, 57 adapted to matingly engage to form va void in which insulation 58, such as ground asbestos, is packed. Sheath 55 has a nger 60 extending therefrom adapted to interlock with a notch 61 in one flange 51 of spool 33. By this means relative rotation between Vspool 33 and sheath 55 is prevented.V The sheath 55 is maintained snugly about the spool 33 by screw 62 extending transversely through extensions 57, 57.

After the heating coil 52 and sheath 55 are assembled about spool 33, molten silver solder 63 is admitted through an opening 64 in sucient quantity to fill all voids about coil 52. In the place of silver solder, aluminum or other metallic powder may be tamped or packed about heating coil 52. By virtue of the metallic ller the heat generated in coil 52 is efficiently conducted to the core of spool 33, thence to die 39 to heat the sheet metal prior to the dimpling thereof.

Since the forming of the sheet metal at either an excessive or an insufficiently high temperature seriously affects the physical properties thereof, the controls 22 are set to initially supply current to coils 52 to heat die 39 and punch Sil to ya predetermined level, and thereafter intermittently supply adequate current to maintain the forming elements within a specified range of temperatures. To sense the temperatures within the forming elements 39, 50 and to produce a signal to be transmitted to the controls 22, a thermocouple 67, with leads 68 through insulation 58, is aixed within each of the assemblies 1S, 19 at a point proximate the tools 39, 50 and in heat transfer relation therewith. By correlating the temperature to which the sheet material is subjected in the first stage yof the forming operation and the duration of the first stage, the temperature to which the sheet is raised can be accurately predetermined.

As apparent by viewing Figure 2, each of the upper and lower die assemblies i8 and 19 essentially consists of three parts, namely a support to be aixed within the machine base, a heating sect-ion and a forming tool, all of which are releasably joined together. By virtue of this arrangement various sizes and shapes of dies can be readily interchanged, and burned out or otherwise damaged heating units can be replaced without necessitating the discarding of all parts of the assembly.

In using the apparatus for the dimpling of flat sheets, there are not parts of the heater unit protruding in the zone occupied by the sheet as to interfere therewith when contacted by the dimple dies. However, when dimpling within narrow concavities of irregularly or compleXly configured stock material, such as channels, flat sections, and angles, at least one die part must freely enter such concavities. While the diameter of the spool member 33 could be reduced to enable its entry, it has been determined, from design and efficiency considerations, that the provision ot the narrow extension 37, at least equal in length t0 the depth of the concavity, is the better means of preventing interference. While the die tool is spaced slightly from the heat source by the extension 37, the heat differential between the upper and lower extremities of extension 37 is not sufhciently large to cause a noticeable drop in the die tool itself.

While the invention has been described with reference to the embodiment herein shown, it is to be understood that it is susceptible to changes and renements within the scope of the appended claims.

We claim:

l. A dimpling machine comprising: a punch; a die cooperating with said punch for forming a dimple shaped depression in sheet-like material; means supporting the punch and die in the machine; means for heating the punch and die and including a spool-like member interposed between each of said punch and die and its respective supporting means, the spool-like member having an annular concavity closed by an encircling sheath, said concavity having therein a resistance type heater embedded in a mass of heat conductive material; means for relatively moving the punch and die toward each other in two phases, the rst of said phases effecting the heat transfer contact of the punch and die with a piece of sheetlike material therebetween and the second of said phases effecting the formation of a depression in the piece of sheet-like material.

2. A heated dimple die comprising: a heat conductive die support having two spaced apart annular flanges and a core extending between the flanges and integral therewith, said core and flanges forming a spool-like member including an annular concavity, said flanges having opposed faces each with a circumferential groove therein; a flexible sheath encircling said core and having marginal edges thereof respectively seated in the circumferential grooves whereby to close said concavity; a heater element within said concavity and encompassing said core; a heat conducting packing about said heater clement for :conducting heat to the core; a mounting base affixed to one of said flanges for attachment to the frame of a dimpling machine and transmitting impact blows between said machine and said die support; a dimpling tool attached to the other of the flanges, said tool impacting through the die support and being heated by heat conducted through the core and said other flange, the heat and impact blows being used for deforming sheet material; and means effecting alignment of said dimpling tool with said mounting post.

3. A heated dimple die comprising: a heat conductive die support having two spaced apart annular flanges and a core extending between the flanges and integral therewith, said core and flanges forming a spool-like member including an annular concavity; a flexible sheath encircling said core and having marginal edges thereof respectively engaging said flanges whereby to close said concavity; a heater element within said concavity and encompassing said core; a heat conducting packing about said heater element for conducting heat to the core; a mounting base aflixed to one of said flanges for attachment to the frame of a dimpling machine and receiving impact blows therefrom for transmission to the die support; a dimpling tool attached to the other of the flanges, said tool receiving impacts through the die support and being heated by heat conducted through the core and said other flange, the heat and impact being used for deforming sheet material; and means eecting alignment of said dimpling tool with said mounting base.

4. A heated dimple die comprising: a heat conductive die support having two spaced apart annular flanges and a ycore extending between the flanges and integral therewith, said core and flanges forming a spool-like member including an annular concavity, said flanges having opposed faces each with a circumferential groove therein; a flexible sheath encircling said co-re and having marginal edges thereof respectively seated in the circumferential grooves whereby to close said concavity; `a heater element within said concavity and encompassing said core; a heat conducting packing about said heater element for conducting heat to the core; a mounting post and platform affixed to one of said flanges for attachment to the frame of a dimpling machine and receiving impact blows therefrom for transmission to the die support; a dimpling tool removably attached to the other of the flanges, said tool receiving impacts through the die support and being heated by heat conducted through the core and said other flange, the heat and impact being used for deforming sheet material; means effecting alignment of said dimpling tool with said mounting post; and a heat sensing means in said other flange adjacent said dimpling tool for controlling said heater element whereby said tool may be removed Without necessitating removal of the heat sensing means from the flange in which it is mounted.

5. A heated dimple die comprising: a heat conductive die support having two spaced apart annular flanges and a core extending between the flanges and integral therewith, said core and flanges forming a spool-like member including an annular concavity, said flanges having opposed faces each with a circumferential groove therein; a flexible sheath encircling said core and having marginal edges thereof respectively seated in the circumferential grooves whereby to close said concavity; a heater element within said concavity and encompassing said core; a heat conducting packing about said heater element for conducting heat to the core; a mounting post and platform afllxed to one of said flanges for attachment to the frame of a dimpling machine and receiving impact blows therefrom for transmission to the die support; a dimpling tool attached to the other of the flanges, said tool receiving impacts through the die support and being heated by heat conducted through the core and said other flange, the heat and impact being used for deforming sheet material; and means effecting alignment of said dimpling tool with said mounting post.

6. For use in a dimpling machine employing heated forming tools, a tool heater and support adapted to be interposed between the tool and frame of the dimpling machine, comprising: two spaced apart generally circular flanges; a core of lesser cross-section than said flanges extending therebetween and being integral therewith whereby a spool-like member is formed having an anular concavity; an insulated heater coil closely encircling the core and having the ends thereof projecting approximately radially therefrom in a common plane; a sheath of flexible material wrapped about said flanges and closing said concavity to form a chamber housing the heater coil, said sheath having end portions extending outwardly from said `core and enclosing the radially projecting ends of the coil; a mass of heat conducting metal encompassing the heater coil and substantially filling the chamber whereby to conduct heat from the heater to the core and flanges; electric leads connected to the ends of the heater coil for connection with a source of power; and a packing of heat and electrical insulation lling voids in the enclosure formed by the end portions of the sheath.

7. For use in a dimpling machine employing heated forming tools, a tool heater and support comprising: two spaced apart generally circular flanges; a core extending between the flanges and forming a spool-like member therewith; an insulated heater coil encircling the core; a sheath of flexible material wrapped about said flanges and forming a closed concavity with the core, said coil being within the concavity; a mass of heat conducting metal filling the voids in the concavity and forming a packing about the coil; and means in each of said flanges for the, respective attachment thereto of a metal forming tool and attaching means to be received by the dimpling machine, the said flanges and core being adapted to transmit pressural impulses between the metal forming tool and the attaching means.

References Cited in the le of this patent UNITED STATES PATENTS 1,589,843 De Lisle June 22, 1926 1,767,607 Moulthrop Tune 24, 1930 2,101,445 Moore Dec. 7, 1937 2,372,516 Rechton et al Mar. 27, 1945 2,582,481 Dvorak et al. Jan. 15, 1952 FOREIGN PATENTS 339,636 Germany July 29, 1921 

